In conveyor belt units with large belt widths and high conveying speeds, individual idlers, because of their dead weight, can no longer be replaced by hand in case of needed repairs.
Auxiliary devices, which are displaceable along the conveying route either next to the belt conveyor, on the belt conveyor or enclosing the belt conveyor in a gate-like manner, are used for replacing worn or damaged idlers. Besides the conveying unit, idler replacement devices, which are displaceable and are each provided with a lifting apparatus, are known, for example, from the publications DD 38 147 A1 and DE 3 42 000 A1. These auxiliary devices are conveyed to the idler station in question, then stopped there and brought into position. The idlers or idler garlands in question are then replaced. For this, a sufficient free space is needed next to and above the belt conveyor.
A vehicle equipped with a lifting means, which is displaceable next to a belt conveyor over its entire length, is known from the publication DE 7 238 731 U. It is equipped with a telescopic extension arm, which accommodates a belt carrier in the horizontal position. This belt carrier is equipped with two auxiliary idlers, which can be adapted in their slope to the trough of the belt. The belt carrier is guided under the belt for lifting the belt from the side opposite the vehicle and lifted to the extent that a sufficiently large free space forms for replacing the idlers lying under it. Due to the auxiliary idlers arranged on the belt carrier, the belt conveyor does not need to be stopped here. The worn idlers may now be replaced. Provided that the work safety regulations applicable for the respective belt conveyor permit, this may also happen during an operation in process. After the replacing, the belt is lowered again and the conveying operation may take place in the manner intended. Sufficient space is needed on both sides of the belt conveyor for the use of this auxiliary device for lifting the belt and replacing the idlers.
A device displaceable on the conveying unit for replacing idlers in the upper run is known from the publication DD 287 919 A5. It consists of a frame equipped with running wheels as a replacing device, which is displaceable under the idlers to be replaced along the supporting structure on both sides. The drive takes place by means of a cable line. Because of the cable line drive, such a solution is suitable for shorter conveying sections, as they are known, for example, from belt bridges or from driving and tensioning stations. It cannot be used in conveyor units that consist of individual sections not mechanically connected with one another.
An idler replacing device for shiftable conveyor belt units is known from the publication DD 229 662 A1. It encloses the conveyor unit in a gate-like manner and is displaceable on the shifting tracks that are present. The idler replacing device is provided with its own drive, by means of which the device is conveyed to the idler station with worn or damaged idlers. In the lifted state of the conveyor belt, the idlers located under it can be replaced. The removed damaged idlers are placed into a magazine arranged on the side of the device, in which new idlers to be replaced are also stored and kept ready. Sufficient space must be present for this magazine next to the conveyor unit over the entire length of use.